As packaging materials, packaging materials in which a polyolefin-based resin film is laminated as a sealant layer on a barrier layer made of, for example, aluminum foil are frequently used. In general, the sealant layer is laminated on the barrier layer, through the intermediary of an adhesive layer (also referred to as, for example, a primer or an anchor coat).
However, when by using such packaging materials, a highly-irritating content such as a substance having volatility such as menthol or naphthalene, a content containing a fragrance component or a medicinal component, or a secondary battery containing a solid organic electrolyte is packaged, during storage of the package, such a substance or such a component affects the adhesive layer between the barrier layer and the sealant layer, and hence, the adhesion strength between the barrier layer and the sealant layer is disadvantageously degraded with time, or both layers peel off from each other (delamination).
Accordingly, in order to solve such problems as described above, JP11-254595A, JP2001-322221A and JP2008-127042A have proposed techniques for improving in the packaging materials the resistance against the contents in the packages. Here, “the resistance against the content” means the performance to suppress the degradation of the adhesion strength between the barrier layer and the sealant layer during the storage of the content. Hereinafter, this performance may foe referred to as “the content resistance.”
In order to solve such problems as described above, the applicant of the present application has proposed, in JP2008-120062A, a method in which a specific adhesive layer is formed by applying an aqueous dispersion having a specific composition to a barrier layer and by drying the applied aqueous dispersion, and a sealant layer is laminated through the intermediary of the specific adhesive layer.